This invention relates to an auxiliary-energy-supplied brake slip control system for a vehicular hydraulic brake system with a brake-pedal-operable master cylinder arrangement, a master cylinder piston, and an associated prechamber wherein a feed bore ends for the supply of auxiliary energy into the working chamber of the master cylinder.
A hydraulic brake system (P 35 07 484.1) is known which consists of a pedal-operated brake booster connected with the master cylinder and having a booster piston a booster chamber, wherein, by way of a brake valve, an auxiliary pressure is established which is proportional to the foot pressure. The system includes a pressure medium source which is provided with wheel brakes connected to the master cylinder and with a filling-stage cylinder with a two-stage piston displaceably housed in the stepped bore thereof. A pressure chamber is provided in front of the large stage of the two-stage piston and with a filling chamber arranged in front of the small stage of the two-stage piston. The pressure chamber communicates with the booster chamber and the filling chamber being connected to one of the working chambers of the master cylinder and/or to the brake lines.
In this known brake booster, a non-return valve is connected in the connection line connecting the booster chamber with the pressure chamber of the filling stage cylinder, with the control slide of the brake valve cooperating with a valve body by wat of which the brake valve is connected with the pressure chamber.
Further, an auxiliary-energy-supplied brake slip control system is known (pending U.S. application Ser. No. 836,687 filed Mar. 12, 1986 and corresponding to German application (P 35 08709.9) which is provided with a filling-stage cylinder with a two-stage piston displaceably housed therein and with a pressure chamber provided in front of the large stage of the two-stage piston and with a filling chamber arranged in fron of the small stage of the two-stage piston. By way of a pressure line the filling chamber communicates with one of the working chambers of the master cylinder and/or with a brake line. In this brake slip control system the booster piston plunges into an annular chamber arranged between the master cylinder and the brake booster. The annular chamber communicates with the pressure chamber of the filling-stage cylinder, on the one hand, and with the supply reservoir, on the other hand, with a valve being connected in the pressure medium path from the annular chamber to the supply reservoir. The valve is operable by the pressure in the booster chamber and, in one of its positions, the valve locks the pressure medium passage to the supply reservoir and thus permits the pressure medium to flow from the annular chamber into the pressure chamber of the filling-stage cylinder during the braking operation. In its other position, the valve connects the annular chamber with the supply reservoir.
This known brake system, however, is disadvantageous in that it is comparatively expensive and intricate and voluminous as a special filling-stage cylinder must be provided in addition to the tandem master cylinder and to the hydraulic brake booster, respectively.
It is thus an object of the present invention to provide a brake system of the foregoing type which, upon a failure of the booster, will work with a reduced effective master brake cylinder surface, which will have a particularly simple design, and which will enable a narrow and largely compact construction.